The purpose of this research study is to more accurately measure the amount of true red blood cell breakdown (hemolysis) in newborn babies with potentially problematic blood type mismatch with their mothers (ABO incompatibility), and to examine how the true level of red blood cell destruction relates to other laboratory tests obtained in newborns with jaundice.

A better understanding of the true amount of red blood cell destruction that is caused by blood type mismatch, as well as how it relates with other laboratory tests ordered for ABO incompatibility and red blood cell destruction, would help avoid unnecessary testing, treatment and prolonged hospital stays in such babies.

Clinically severe jaundice due to ABO incompatibility can occur when infants with blood type A or B are born to mothers with type O blood. An estimated 20 percent of pregnancies are ABO incompatible, but only a very small proportion of blood type A or B babies born to O type mothers develop overt ABO hemolytic disease. Despite the relative rarity of ABO hemolytic disease, it is common practice among pediatricians and family practice physicians to perform routine blood typing and antibody screening on all newborns born to type O mothers.

A very accurate and reliable laboratory measure of red blood cell destruction is the plasma carboxyhemoglobin level (COHb). COHb levels can be determined using a minute amount of blood, obtained at the same time the newborn's heel is pierced to obtain blood for the mandatory newborn screen (performed on all newborns prior to discharge) in order to avoid an additional invasive procedure.

Our hope is to determine whether routine blood typing and anti-globulin testing of infants born to type O mothers is necessary, or if these tests should instead be obtained only in the context of significant visible jaundice. This would help clarify the proper management of a very common problem in the newborn, and minimize the potential for subjecting infants of type O mothers to unnecessary blood tests, unwarranted treatment, and prolonged hospitalizations.

significant birth trauma with continued bruising and/or sequestration of blood still evident at the time of discharge

known perinatal blood loss with hemodynamic consequences such as persistent tachycardia, need for fluid boluses or supplemental oxygen

neonatal anemia with Hb<13.5g/dL

known family history of hereditary hemolytic disease such as G6PD deficiency, hereditary spherocytosis or hereditary elliptocytosis

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Please refer to this study by its ClinicalTrials.gov identifier: NCT00917007